Chip cards are subjected to mechanical bending forces in daily use. These bending forces act on the card for example during transport, whether while they are being shipped or while they are being kept in a billfold, and can lead to permanent damage. Even if a card body is relatively insensitive to these flexural loads, the reversible deformations of the card that occur may lead to detachment of terminal contacts of the chips contacted in the card body, whereby the functionality of the card is destroyed.
The bending forces usually act on opposite sides of the chip card in such a way that the vertex of a bending line runs along one of the axes of symmetry of the chip card.
In particular in the case of chip cards with contact areas, the flexural loading may lead to permanent damage of the chip card. Chip cards with contact areas comprise the card body with a cavity, in which a chip module with a chip and contact areas is arranged in such a way that the contact areas are accessible from the outside and terminate as flush as possible with the surface of the card.
For reasons of symmetry and to simplify production, in the case of conventional chip modules the chip is positioned centrally in a region comprising the contact areas.
The deformation during bending of the card has the effect that the bending forces are transferred to the chip module incorporated in the card body. Deformation of said chip module may damage a connection between the terminal areas of the chip and the contact areas.
Previous attempts to increase the robustness of a chip card with respect to the dynamic bending stress are aimed at optimally matching the material composition of the chip card structure and of reducing and/or absorbing the bending stress that is transferred to the module. This takes place for example by using a highly flexible supporting material and a flexurally more rigid encapsulating material with very good adhesion with respect to the supporting material and the chip. This is intended to prevent the delamination, the detachment of the chip or its terminal areas, caused by the bending stress that is introduced.
With the widespread use of chip cards in a large number of application areas, standardized chip cards are often used, making it possible for chip cards and chip card reading and writing devices from different manufacturers and for different applications to operate together without any problem.
The arrangement of the contacts on a chip card usually conforms to ISO standard 7816/2. According to the standard, the contact areas are arranged on the axis of symmetry of the chip card running in the longitudinal direction. The bending forces often act on the longitudinal sides or on the transverse sides of the chip card. In the case of bending forces acting on the longitudinal sides of the chip card, the vertex of the bending line runs along the axis of symmetry of the longitudinal direction, so that in. this case the greatest deformation occurs along this axis of symmetry.
In the case of the standardized chip cards known from the prior art, the greatest curvature of the bending line runs in the direct vicinity of the chip. Therefore, the deformations that are caused by bending and the resultant delamination forces are particularly great along the vertex line and may damage the sensitive contacting.